An object of the present invention is to trace a user who has deposited bills as counterfeit bank notes into an ATM. The ATM having a bill deposit function judges a denomination and genuineness of bills deposited by the user by a validator, extracts bill information and stores in a search DB its bill information to be matched with an account number of the user (first data). It stores, in a trace DB, bill information of bills judged as counterfeit bank notes by the validator (second data). The search DB is searched with the second data as a key to extract similar bill data for specifying, from a result, the user who has used the bills as counterfeit bank notes.